1. Field of the Invention
The present invention relates to an air pressure sensor, and in particular, to a vibration-type air pressure sensor.
2. Related Art
As an air pressure sensor for measuring air pressure, a vibration-type air pressure sensor, as disclosed in Japanese Patent No. 3191459 (Patent Document 1), has been known. A vibration-type air pressure sensor measures the natural frequency of a vibrator, which varies depending on the pressure of a gas, by using a piezoelectric device to thereby measure the air pressure. Such an air pressure sensor is used to measure the height, for example.
[Patent Document 1] JP 3191459 B
However, a vibration-type air pressure sensor involves temperature drift, that is, the sensor has such a feature that the characteristics of a piezoelectric device for measuring the natural frequency of a vibrator changes corresponding to the temperature. This causes a problem that a measurement error may be caused as the surrounding temperature changes. Specifically, in a PZT, the natural frequency to be detected changes by 3 kHz in a range from 20 to 85°. In particular, the amount of change increases in the high temperature side. In the case of using the air pressure sensor in an altimeter, if a measurement error of 3 kHz is caused, an error of 300 m may be caused, which results in a problem of low measurement accuracy.